Group buying is an Item is at full price or unavailable until X amount of customers buy the product, once X amount is reached product is at discount price or available for purchase.
Brenda Lee commented
Did you try Boost Sales app in Beeketing plugin? They have the last step up-sell feature that could do the same thing as you want.
You can set a condition of cart value or cart item so that only when customers reach your goal, they will be able to see the discounted product.
You can install the plugin here: https://beeketing.com/beeketing-for-woocommerce?utm_channel=referral&utm_medium=forum&utm_term=ideaswc
I hope this helps.